1. Field of the Invention
The present invention relates to a vehicle height control system having an improved control means controlling vehicle height at the start of the vehicle.
2. Description of the Prior Art
According to the conventional system, vehicle height at the start of the vehicle is controlled in the following procedure. Usually, the height of a vehicle is detected and vehicle height adjustment is started upon the lowering of the vehicle height owing to the boarding of passengers. A vehicle height judging time for deciding whether or not vehicle height adjustment should be carried out is set beforehand. That is, a vehicle height judging time for starting is comparatively short so that a target vehicle height can be restored quickly even if the vehicle height varies due to the alighting and boarding of passengers while the vehicle is stopping, while a vehicle height judging time for running is longer than the vehicle height judging time for starting to obviate frequent vehicle height adjustment at every temporary variation of the attitude of the vehicle resulting from running on an irregular road, or acceleration or deceleration of the vehicle. On the other hand, vehicle height adjusting operation is stopped as soon as the vehicle height has reached the target vehicle height so that the vehicle height will not exceed the target vehicle height.
If the vehicle is started and accelerated in course of vehicle height adjusting operation, the front side of the vehicle is raised by the inertial force over the target vehicle height, and thereby the vehicle height adjustment for the front side is interrupted. Consequently, the front side lowers of itself after the starting acceleration has been completed and the running mode has been transferred to a constant-speed running mode, and hence the height of the front side becomes lower than the target vehicle height.
Since the vehicle height judging time for running is comparatively long to obviate the frequent vehicle height adjustment during running as noted above, the vehicle is obliged to run for a long time with the front side dipping even after the transition of the running mode from acceleration to constant-speed running and it takes long time to make the vehicle height of the front side coincide with the target vehicle height, when the vehicle is started to run with the front side dipping.